Magneto doesn't come across as holding back in X-Men #1, no matter what the recons might claim.
Well they obviously wouldn't have the experience. Though they would have the training. Almost every issue of X-Men from the era the kids are from features a training session on the Danger Room. In their first 10 issues they fought Magneto,Vanisher, the Brotherhood, the Blob, Unus, Namor, the Avengers ( the original line) and Ka-Zar. They got experienced pretty fast.